A telecommunication exchange of the type mentioned is described in the publication "A PABX concept combining a new method of decentralized control and PCM switching", International Switching Symposium, Paris 1979. With respect to conventional telephony it enables a large number of different functions, e.g. intercom, TELEX, video communication, data communication etc. and is modularly extendable without resorting to intervention in the existing modular line units.
In putting an exchange with a number of modules into service the program must be written into each of the memories. This question is time consuming, since in transferring data information from a tape recorder, for example, the recorder must be connected in turn to each of the modules which are not necessarily in the same building, but may be mutually spaced at distances in the order of magnitude of one kilometer from each other.